Area Forecast Discussion
Issued by NWS Portland, OR

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FXUS66 KPQR 202125
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
222 PM PDT SUN APR 20 2014

.SYNOPSIS...A SERIES OF UPPER TROUGHS WILL BRING MUCH COOLER AND
WETTER CONDITIONS FOR MUCH OF THE UPCOMING WEEK. THE NEXT PACIFIC
COLD FRONT WILL APPROACH THE REGION MON AND MOVE THROUGH MON NIGHT.
SHOWERS CONTINUE ON TUESDAY WITH SNOW LEVELS LOWER TO AT OR BELOW
PASS LEVEL. A WARM FRONT APPROACHING THE COAST WILL KEEP A THREAT FOR
SHOWERS GOING WED...THEN ANOTHER COOL SHOWERY TROUGH IS EXPECTED FOR
THE LATTER HALF OF THE WEEK.
&&

.SHORT TERM...TONIGHT THROUGH WEDNESDAY...READINGS GETTING INTO THE
60S WITH A MIX OF SUN AND INCREASED HIGH CLOUDINESS UNDER SOMEWHAT
FLAT TO SLIGHTLY SW FLOW ALOFT THAT IS CONTINUING TO AMPLIFY. EXPECT
TO TOP OUT IN THE MID 60S. THE CLOUDS ARE COURTESY OF OUR NEXT MAIN
WEATHER MAKER THAT WILL TAKE THE PACIFIC NORTHWEST INTO A PERIOD OF
COOL AND UNSETTLED CONDITIONS FOR MOST OF THE WEEK.

THE FEATURE TO THANK IS A DEEP UPPER LOW IN THE GULF OF ALASKA. THE
FIRST DISTURBANCE WRAPPING AROUND THIS LOW IS PUSHING NORTH INTO B.C.
AND WE ARE GETTING THE HIGH CLOUDS FROM THIS. THE UPPER JET WILL
ROUND THE BASE OF THIS UPPER LOW TONIGHT AND PUSH THE WHOLE TROUGH
AXIS CLOSER TO THE REGION ON MONDAY. AT THE SURFACE...A COLD FRONT
AND ITS ASSOCIATED MOISTURE FEED AHEAD OF THE UPPER LOW SLOWLY NEARS
THE COAST LATE TONIGHT INTO EARLY MONDAY AS THE UPPER FLOW BECOMES
PARALLEL TO THE SURFACE FRONT. CONSISTENT SIGNAL IN THE MODELS FOR
PRECIPITATION AHEAD OF THE COLD FRONT TO REACH THE COAST IN THE
MORNING...WHILE SOUTHWEST FLOW AND DISTURBANCES MOVING NORTH ON THE
FRONT SIDE OF THE DEEP UPPER TROUGH OFFSHORE HAVE THE MODELS KICKING
OUT SOME SHOWERS IN THE CASCADES. MOST MODEL GUIDANCE SUGGEST THE
POTENTIAL FOR SOME SHOWERS AS EARLY AS THE LATE MORNING BUT ARE MORE
CONSISTENT FOR THE AFTERNOON. MODEL SOUNDINGS ARE MIXED WITH REGARDS
TO THUNDER POTENTIAL IN THE AFTERNOON. NAM BUFR SOUNDINGS SHOW LITTLE
TO NO CAPE AND THE GFS SHOWING A BIT MORE...BUT NEITHER IS VERY
IMPRESSIVE.

THE COLD FRONT AND UPPER TROUGH PUSH ONSHORE IN THE EVENING WHILE THE
CORE OF THE UPPER LOW CIRCULATION REMAINS OFFSHORE. THIS WILL BE THE
FIRST PUSH OF MORE ORGANIZED RAIN/SHOWER ACTIVITY. SNOW LEVELS LOWER
TO THE PASSES BY TUESDAY MORNING. THEN THE FIRST TROUGH AXIS AND
RELATED COLD POOL SHIFTS INLAND TUESDAY. EXPECT THIS COULD BE DAY TO
SEE QUITE A BIT OF SHOWERS AND TOWERING CUMULUS AND POSSIBLY
ISOLATED THUNDER. HAVE ADDED SOME THUNDER TO THE SOUTH OF THE AREA
CLOSER TO MORE ORGANIZED FORCING. AN ARGUMENT COULD BE MADE THAT
THIS AREA COULD BE EXPANDED..AND WILL LET FUTURE SHIFTS SEE IF
INSTABILITY PARAMETERS IMPROVE A LITTLE. WITH 850 TEMPS BELOW
ZERO...LOOKS LIKE BELOW NORMAL HIGHS IN THE 50S. THEN THE MAIN UPPER
LOW OFF THE WASHINGTON COAST MOVES INLAND THROUGH WASHINGTON STATE
TUESDAY NIGHT...BRINGING ANOTHER ORGANIZED RAIN AND MOUNTAIN SNOW.
SEVERAL INCHES OF SNOW ARE EXPECTED EVEN AT PASS LEVEL...ESPECIALLY
TUESDAY NIGHT...WITH AMOUNTS OVER 6 INCHES AT THE HIGHEST ELEVATIONS
LATER MONDAY NIGHT THROUGH EARLY WEDNESDAY. THE PASSES HAVE BEEN
BARE FOR A WHILE NOW SO CAUTION IS URGED FOR THOSE TRAVELING THE
PASSES.

OH BUT THE FUN IS NOT OVER YET. AFTER BRIEF RIDGING...ANOTHER TROUGH
IS ON THIS ONES HEELS AND READY TO TAKE OVER. THE ACTION BEGINS WITH
A WARM FRONT AHEAD OF THE UPPER LOW WEDNESDAY. LOOKS LIKE ANOTHER WET
DAY WITH PRECIPITATION FALLING AS RAIN EVEN IN THE CASCADES. /KMD

.LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY...THE EXTENDED FCST
PERIOD CONTINUES TO LOOK CLOUDY...COOL...AND WET. MODEL AGREEMENT IS
GOOD THAT A WARM FRONT WILL BRING INCREASING RAIN WED NIGHT INTO
EARLY THU...WITH THE TRAILING COLD FRONT MOVING THROUGH DURING THE
DAY ON THU. IT APPEARS THAT THERE WILL BE PLENTY OF SHOWERS AROUND
LATER THU AND FRI AS THE PARENT UPPER LEVEL TROUGH MOVES THROUGH THE
PAC NW. WE MAY ALSO NEED TO WATCH FOR ISOLATED THUNDERSTORM
POTENTIAL DURING THIS TIME AS THE COLD POOL ASSOCIATED WITH THE
UPPER TROUGH PASSES OVER THE REGION. EXPECT SHOWERY CONDITIONS TO
CONTINUE THROUGH NEXT WEEKEND. A SHORTWAVE TROUGH IS MODELED TO MOVE
ONSHORE SOMETIME LATER SAT OR SUN...WHICH WILL LIKELY BRING A ROUND
OF MORE ORGANIZED PRECIPITATION. PYLE

&&

.AVIATION...VFR CONDITIONS PREVAILING WITH SEVERAL CLOUD LAYERS.
THE LOWER AROUND 4000 FT WITH A CIRRUS LAYER ABOVE. A FRONT
OFFSHORE WILL CONTINUE TO FEED MOISTURE INTO THE AREA BUT EXPECT
VFR CONDITIONS THROUGH MON MORNING. HOWEVER...FOR THE COASTAL
AREAS MVFR CONDITIONS LIKELY LATE TONIGHT AND MON AS THE FRONT
APPROACHES.

KPDX AND APPROACHES...VFR PREVAILING FOR THE NEXT 24 HOURS.

&&

.MARINE...LARGE WESTERLY SWELL TRAIN CONTINUES TO SUBSIDE THIS
AFTERNOON BUT WILL REMAIN IN THE 14 TO 17 FT RANGE THIS EVENING
THEN NEAR 12 FT MON MORNING THEN HOVERING NEAR 10 FT FOR MOST OF
THE WEEK. THE SMALL CRAFT FOR HAZARDOUS SEAS CONTINUE THROUGH
MON NIGHT.

A RELATIVELY QUIET PERIOD IN TERMS OF WIND OVER THE WATERS
THROUGH THE FIRST HALF OF THIS WEEK. A WEAK SYSTEM WILL APPROACH
THE WATERS THIS AFTERNOON AND COULD BRING A FEW OCCASIONAL GUSTS
TO 20-25 KT OVER THE FAR NORTHERN OUTER WATERS . OTHERWISE...THE
NEXT SIGNIFICANT SYSTEM ARRIVES LATE WED OR THU...LIKELY BRINGING
SMALL CRAFT WINDS.

&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 5 AM PDT
     TUESDAY FOR COASTAL WATERS FROM CAPE SHOALWATER WA
     TO FLORENCE OR OUT 60 NM.

     SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR
     UNTIL MONDAY AFTERNOON.

&&

$$

MORE WEATHER INFORMATION ONLINE AT...
    HTTP://WEATHER.GOV/PORTLAND

INTERACT WITH US VIA SOCIAL MEDIA
    WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.PORTLAND.GOV
    WWW.TWITTER.COM/NWSPORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA..


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